Energy distribution detector for microwave oven



April 25, 1967 N. J. PANSING ENERGY DISTRIBUTION DETECTOR FOR MICROWAVE OVEN Filed April 50, 1964 palm)? BY INVENTOR J P02757729 H16 ATTORNEY United States Patent 3,316,380 ENERGY DISTRIBUTION DETECTOR FOR MICROWAVE OVEN Nelson J. Pansing, Clayton, Ohio, assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Filed A r. 30, 1964, Ser. No. 363,716 Claims. (Cl. 21910.55)

This invention relates to a domestic appliance and more particularly to an energy detector and safety shelf for a microwave oven.

In microwave cooking it is essential that the oven be safe for domestic use. In addition, cooking results depend in large measure on the uniformity of distribution of microwave energy throughout the oven chamber. This invention is directed to a food support shelf for use in a microwave oven which accomplishes the dual function of informing the operator whenever microwave energy exists in the oven and whether or not the microwave energy is distributed sufliciently uniformly throughout the oven for good cooking results.

Accordingly, it is an object of this invention to provide a support shelf in a microwave oven which is adapted, by the fluorescence thereof, to indicate the presence and pattern of microwave energy in the oven.

Another object of this invention is the provision in a microwave oven of a compartmented glass-like shelf for supporting foods to be cooked, the compartments of said shelf being constructed like a fluorescent lamp to include a first substance in the cavity of the compartment to produce ultraviolet light radiation in the presence of microwave energy and a second substance on the walls of said compartments which fluoresce in response to said ultraviolet light radiation.

A further object of this invention is the provision of a fluorescent test shelf usable in a microwave oven for testing the distribution or pattern of microwave energy in the oven.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings wherein a preferred embodiment of the present invention is clearly shown.

In the drawings:

FIGURE 1 is a side elevational view of a range with parts broken away to show a microwave oven suitable for use with this invention;

FIGURE 2 is a perspective view of a food support shelf formed in accordance with the teachings of the invention;

FIGURE 3 is a fragmentary sectional view taken along line 33 in FIGURE 2.

FIGURE 4 is a fragmentary sectional view taken along line 44 in FIGURE 3.

In accordance with this invention and with reference to FIGURE 1, an electric range is illustrated having an inner liner 12 forming a microwave oven cavity 14 closable at the front thereof by a door 16. In a portion of the range remote from the oven cavity there is a source of microwave energy, shown here by way of example as a magnetron 18 coupled to said oven through a coupling arrangement 20 for conveying the microwave energy to the oven cavity 14.

The concept of this invention is directed to a novel combination test and support shelf 22 slidably positioned on embossments 24 on the sides of the oven liner 12. The shelf 22 is made slidably removable from the oven cavity 14 when the door 16 is opened. With reference to FIGURES 2, 3 and 4, the oven shelf 22 is shown comprised of a closed glass-like envelope having in the interior thereof a plurality of independent pockets or compartments 26. The compartments 26 are formed in the 3,316,380 Patented Apr. 25, 1967 center of a glass sandwich having an upper glass layer 28 and a lower glass layer 30. When the glass layers are positioned together, the various compartments 26 are completely sealingly segregated one from the other and from the atmosphere so that each forms, in effect, a small box-like fluorescent lamp. The peripheral edge of the shelf may also be sealed by a glass bead 31 to insure the isolation of the compartments 26 from the atmosphere.

More particularly, each pocket 26 contains a quantity of argon gas and mercury vapor therein. The glass layer portions 32 forming the walls of each compartment 26 are coated with a chemical which fluoresces in the presence of ultraviolet light radiation. Following are chemicals or phosphors suitable for use in coating the walls of the compartments 26 along with the color produced in response to ultraviolet light radiation:

Phosphor: Color Calcium tungstate Blue. Magnesium tungstate Blue-white. Zinc silicate Green.

Zinc berylliumsilicate Yellow-white. Cadmium silicate Yellow-pink. Cadmium borate Pink.

360 BL phosphor Blue ultra. E phosphor Do.

In operation, microwave energy present in the oven cavity 14 excites the argon gas and mercury vapor in each compartment 26 in proportion to the amount of microwave energy present in the vicinity of the particular compartment. This excitation produces ultraviolet light radiation which impinges on the fluorescent chemicals on the walls of each compartment 26, causing the chemicals to fluoresce and emit light. present at a particular shelf location, the brighter will glow the compartments at this location. The color of the light, depending upon the chemicals used, may be predetermined in accordance with the above chart.

Since a microwave oven door 16 may be provided with a grille-like means for seeing into the oven cavity, the operator is informed by the lighted or darkened condition of the oven shelf as to the presence or absence of microwave energy. Thus, a safety feature is effected whereby injury is prevented to one who might otherwise reach into the oven.

In addition to the safety feature of this invention, the uniformity of the light pattern evidenced on the oven shelf indicates the distribution of microwave energy along. the oven cross-section defined as subdivided by the oven shelf. If one portion of the shelf glows more brightly than another portion thereof, an indication is given of improper microwave energy distribution and suitable adjustments may be made to correct this situation. Thus, uniform cooking results may be assured. This facet of the invention has particular utility in the manufacture of microwave ovens as a quality control device to preset the microwave pattern in the oven.

While the embodiment of the present invention as herein disclosed constitutes a preferred form, it is to be understood that other forms might be adopted.

What is claimed is as follows:

1. Cooking apparatus comprising an oven consisting of a metallic enclosure, means for radiating high frequency electromagnetic waves of a predetermined wave length to the interior of said oven, said oven having an aperture in one wall thereof, and support means in said oven slidably removable through said aperture, said support means including a glass shelf having a plurality of compartments, each of said compartments enclosing means illuminated in response to radiated electromagnetic waves whereby to serve as an indicator for the presence or absence of said electromagnetic waves.

The more microwave energyv 2. Cooking apparatus comprising an oven consisting of an enclosure, means for radiating high frequency electromagnetic waves of a predetermined wave length to the interior of said oven, and support means in said oven for supporting food to be cooked, said support means including a shelf having a plurality of compartments, each of said compartments enclosing means illuminated in response to radiated electromagnetic waves whereby to serve as an indicator for the presence or absence of said electromagnetic Waves.

3. The cooking apparatus of claim 2 wherein the illuminated means includes gaseous means in the void of each of said compartments capable of producing ultraviolet light radiation in response to radiated electromagnetic waves and phosphor means on a wall of each of said compartments capable of fluorescing to emit light in response to said ultraviolet light radiation.

4. A support shelf adapted for use in an electromagnetic wave oven for providing a test pattern indicative of a distribution of electromagnetic Wave energy at dififerent locations on said shelf as a measure of cooking efficiency at said locations, and comprising means forming a shelf having a plurality of airtight, independent compartments, said shelf having a characteristic for supporting foods to be cooked, and means in said compartments illuminated in response to radiated electromagnetic wave energy, each of said compartments independently illuminating in a degree proportional to the amount of said energy present in the location on said shelf of the respective pocket whereby to provide a visual indication of energy distribu- References Cited by the Examiner UNITED STATES PATENTS 2,644,113 6/1953 Etzkorn 313-108 X 2,831,952 4/1958 Warner 21910.55 X 2,933,648 4/1960 Bentley 315169 2,961,520 11/1960 Long 21910.55 3,207,906 9/1965 Oikawa 313-108 OTHER REFERENCES German application 1,120,619, printed December 1961 (K1 21h36), Schwenkhagen.

German application 1,133,048, printed July 1962 (K1 21h36), Sohns.

German application 1,133,049, printed July 1962 (K1 21h36), Sohns.

RICHARD M. WOOD, Primary Examiner.

L. H. BENDER, Assistant Examiner. 

1. COOKING APPARATUS COMPRISING AN OVEN CONSISTING OF A METALLIC ENCLOSURE, MEANS FOR RADIATING HIGH FREQUENCY ELECTROMAGNETIC WAVES OF A PREDETERMINED WAVE LENGHT TO THE INTERIOR OF SAID OVEN, SAID OVEN HAVING AN APERTURE IN ONE WALL THEREOF, AND SUPPORT MEANS IN SAID OVEN SLIDABLY REMOVABLE THROUGH SAID APERTURE, SAID SUPPORT MEANS INCLUDING A GLASS SHELF HAVING A PLURALITY OF COMPARTMENTS, EACH OF SAID COMPARTMENTS ENCLOSING MEANS ILLUMINATED IN RESPONSE TO RADIATED ELECTROMAGNETIC 